"Our victim, an 18-year-old man, was waiting for a bus when three males approached him and began attacking him, punching him to the ground inside a bus shelter and continuing to assault him before a man intervened and pulled off one of the attackers.''

Hunter said the trio fled.

Police took the victim to Waikato Hospital where he was admitted for multiple fractures to his jaw. The victim was to have surgery on his face today.

Hunter said CCTV cameras captured the incident and detectives are reviewing the footage.

"While officers were attending the victim at the hospital yesterday, camera operators advised police that one of the attackers had returned to the scene and a 16-year-old boy was arrested a short time later.

"An 18-year-old male has since been identified as one of the other offenders and he is currently actively being sought.''

The third offender was described as a Maori or Polynesian male aged in his late teens to early 20's wearing a black hooded sweatshirt over a black baseball cap with white writing on it.

Hunter said this male was the tallest of the three offenders and of slim build and facial hair on his top lip and chin."

So far only one witness has come forward yet CCTV footage shows there were dozens of people who would have witnessed the attack.

"What we're asking for is that those who saw something do something- come forward to police with what you saw. This type of behaviour is unacceptable anywhere at any time of day but for it to occur in the middle of the city in broad daylight is simply not on."

Hunter praised the bystander who intervened.

"Had it not been for this man's actions the victim's injuries could have been far worse and we would like to acknowledge this person's actions."

Anyone with any information on what happened or who knows the identity of the third attacker is asked to contact Mr Hunter on 07 858 6200.

Alternatively, information can be left anonymously with the independent Crimestoppers on 0800 555111.